Frequency converters are used as static frequency converters for operating electric motors including synchronous and asynchronous machines. The connection of a frequency converter and a motor to form a combined structural unit has advantages with respect to interfering electromagnetic disturbances compared to deployment of the converter in a separate switching cabinet away from the motor.
DE 36 42 724 A1 (corresponds to U.S. Pat. No. 4,963,778) describes a frequency converter for controlling a motor. The converter is arranged in a converter housing that is designated as a terminal box. A power supply-side connection line of the converter, in the form of an attached cable, leads out from the converter housing. An adapter is on the converter housing. The adapter has plug pins for connecting the output side of the converter to contacts of the motor. Installing the converter housing on the motor housing causes of the plug pins to make contact with corresponding sockets on the motor side which are electrically connected with the motor windings.
EP 0 958 646 B1 (corresponds to U.S. Pat. No. 6,229,232) describes a frequency converter for controlling a motor. The converter includes a housing for installation on the housing of the motor and an intermediate component in place of a terminal box. The intermediate box is located between the housings. The intermediate component forms the lower part of the converter housing. The electronics of the converter are contained in the upper part of the converter housing. The electrical connection of the electronics of the converter within the intermediate component is accomplished through plug-and-socket connectors.
The above-noted designs are advantageous for electric motors in the lower to middle power classifications configured to match frequency converters for this purpose. However, other designs are desired for frequency converters for higher powered electric motors as the plug-and-socket connectors are not suitable contact means for the typically encountered current levels.